The hidden quasar nucleus of a WISE-selected, hyperluminous, dust-obscured galaxy at z similar to 2.3

We present the first X-ray spectrum of a hot dust-obscured galaxy (DOG), namely W1835+4355 at z similar to 2.3. Hot DOGs represent a very rare population of hyperluminous (>= 10(47) erg s(-1)), dust-enshrouded objects at z >= 2 recently discovered in the WISE All Sky Survey. The 40 ks XMM-Newton spectrum reveals a continuum as flat (Gamma similar to 0.8) as typically seen in heavily obscured AGN. This, along with the presence of strong Fe K alpha emission, clearly suggests a reflection-dominated spectrum due to Compton-thick absorption. In this scenario, the observed luminosity of L2-10 similar to 2 x 10(44) erg s(-1) is a fraction (